The first submitted version of this puzzle had fifteen rows: the sides of the heart tapered down further so that just a single entry connected the top and bottom halves of the puzzle. That entry also contained an unchecked letter passing between two blocks; I thought it appropriate for that letter to be an 'X' — the symbol for a kiss — but Will rejected the idea of an unchecked letter, so it was back to the drawing board.

The final design clearly has three vertical entries which connect the top and bottom. This was no trivial undertaking. I think I entered over 20,000 words to my word list before coming up with the particular choices for 12-D and 13-D. Ironically, it wasn't until I put GALLIUM into the working part of my word list that the whole fill coalesced.

Getting TENDERHEARTEDLY into the fill was somewhat fortuitous since it initially appeared that nothing thematic was going to work in that spot. I had a list of about 30 valentine-related 15-letter entries to screen.